Generally, as shown in FIG. 1, a conventional RF system, which is used for a multimedia receiver (Set Top Box) for receiving digital broadcast, terrestrial broadcast, satellite broadcast, etc., consists of a plurality of antenna 21 and 22, an RF switching unit 30 and an RF modulator unit 40, wherein the RF switching unit 30 and the RF modulator unit 40 are separated from each other.
The plurality of antenna 21 and 22 receive an inputted RF signal, respectivnely, such as the digital broadcast, terrestrial broadcast, satellite broadcast, etc.
The RF switching unit 30 includes a plurality of input terminals 31 and 32 connected to the respective antenna 21 and 22, an RF relay 33 for switching and selectively outputting RF signal, which have been inputted to the plurality of RF input terminals 31 and 32, on the basis of RF relay control signal inputted from the outside, a first RF amplifier 34 for amplifying RF signal outputted from the RF relay 33, and an RF signal distributor 35 for distributing RF signal amplified and outputted from the first RF amplifier 34.
The RF modulator unit 40 includes an RF input terminal 41 connected to the RF signal distributor 35 within the RF switching unit 30, a second RF amplifier for amplifying RF signal inputted to the RF input terminal 41, an RF modulator 43 for receiving and modulating digital video/audio signal outputted from a digital tuner and demodulator unit 50 within a receiver, which tunes/demodulates inputted RF signal, an RF selection switch 44 for selectively transferring RF signal amplified and outputted from the second RF amplifier 42 or analog tuning signal outputted from the RF modulator 43, and an RF output terminal 45 for outputting signal from the RF selection switch 44.
The operation of such the conventional RF system, in which the RF switching unit and the RF modulator unit are separated from each other as described above, will now be described in detail with reference to FIG. 1.
If the RF relay 33 is switched according to the RF relay control signal to selectively supply the RF signal inputted through the respective antenna 21 and 22 to the first RF amplifier 34, the first RF amplifier 34 amplifies and outputs the RF signal to the RF signal distributor 35.
The RF signal distributor 35 distributes the RF signal inputted thereto. One distributed RF signal is transferred to the RF modulator unit 40, and the other distributed RF signal is transferred to the digital tuner and demodulator unit 50.
The RF signal inputted to the RF modulator unit 40 is amplified by the second RF amplifier 42. At this time, as shown in FIG. 1, if the RF selection switch 44 connects the second RF amplifier 42 to the RF output terminal 45, the amplified RF signal is outputted directly through the RF output terminal 45.
On the other hand, if the RF selection switch 44 connects the RF modulator 43 to the RF output terminal 45, the digital audio/video signal modulated in the RF modulator 43 is outputted through the RF output terminal 45.
At this time, the RF modulator 43 receives the audio/video signal detected in the digital tuner and a demodulator unit 50 (or analog tuner and demodulator unit), and modulates them to a particular analog channel broadcast to output RF signal.
However, in the conventional RF system, in which the RF switching unit and the RF modulator unit are separated from each other, the RF switching unit and the RF modulator unit are constructed in each separated block, respectively. Such construction causes a performance deterioration due to a signal loss or generation of a noise signal resulting from use of same devices (for example, RF amplifier) among the respective block as well as from matching input/output impedance to the respective block.
The conventional RF system of the above construction has another problem of relatively enlarging a product size due to the independent blocks of the RF switch unit and the RF demodulator unit.